< class="breadcumb-title text-anim" data-cue="slideInUp" data-delay="300">PDF Lock
Free PDF Lock Tool — Password Protect PDFs with AES-256 Encryption | ASLI FORM

PDF Lock Tool

Upload a PDF, choose what to protect, set a password and permissions, then download an encrypted file. Everything runs on your device — your document and password are never uploaded.

Drop your PDF here

or click to browse from your device

Supports PDF files up to 100MB · Encrypted locally in your browser

document.pdf
0 pages · 0 MB
0 selected
How selected-page locking works: the PDF standard encrypts an entire file, not individual pages. So the pages you select are gathered into a brand-new PDF and that new file is encrypted — you get a password-protected document containing exactly the pages you chose.
Passwords
Enter a password
The owner password unlocks full control and lets you change permissions later. If blank, we generate one and show it to you after locking.
Encryption & Permissions
AES-256 is the industry standard approved for top-secret data and works in all modern PDF readers.
Other permissions (tick = allow)
Preparing…

World-Class PDF Security Features

Powered by the industrial QPDF encryption engine compiled to WebAssembly, this tool delivers the same AES protection used by enterprise document systems — with zero uploads and zero cost.

  • AES-256 EncryptionThe strongest standard available — approved for top-secret data and virtually impossible to brute-force.
  • AES-128 & Legacy RC4Choose AES-128 for broad compatibility or RC4 for very old PDF readers.
  • Open PasswordRequire a password before anyone can even view the document.
  • Owner PasswordA separate master password that controls permissions; auto-generated if you don't set one.
  • Lock Entire PDFProtect every page of the document with one password in a single step.
  • Lock Selected PagesPick specific pages by thumbnail; they're gathered into a new encrypted PDF.
  • Printing ControlAllow full printing, low-resolution only, or block printing completely.
  • Copy ProtectionStop people from copying text and images out of your PDF.
  • Edit & Annotate LockPrevent modifications, comments, form filling and page reordering.
  • Accessibility OptionKeep the document usable with screen readers while still protecting it.
  • Password GeneratorCreate a cryptographically strong random password in one tap.
  • Strength MeterInstant feedback on how strong your open password is.
  • Quality PreservedEncryption is content-preserving — text, vectors, images and fonts stay crisp and searchable.
  • 100% PrivateFiles and passwords never leave your device. Safe for legal, medical and financial use.
  • Works OfflineAfter the first load, lock PDFs with no internet connection at all.
  • Every DeviceFully responsive from small keypad phones to 4K desktops, with touch and keyboard support.

How to Lock a PDF in 4 Steps

No software to install and no account to create. Password-protect any PDF right in your browser.

  • 1
    Upload Your PDFDrag and drop or browse. You can also pick a file from your phone, tablet or cloud storage.
  • 2
    Choose What to LockProtect the entire document, or switch to Selected Pages and tick the pages you want.
  • 3
    Set Password & RulesEnter an open password, pick AES-256, and decide who can print, copy or edit.
  • 4
    Lock & DownloadClick Lock PDF, then download your encrypted, password-protected file instantly.

Who Needs a Locked PDF?

Whenever a document is sensitive, password protection is the first line of defence.

  • Legal & ContractsProtect agreements, affidavits and filings so only intended parties can open them.
  • Finance & InvoicesSecure payslips, bank statements, tax forms and confidential reports.
  • HealthcareEncrypt prescriptions, lab reports and patient records for HIPAA-style privacy.
  • EducationProtect answer keys, certificates and proprietary course material from copying.
  • Real EstateLock lease deeds, property documents and KYC papers before sharing.
  • Personal DocumentsSafeguard IDs, resumes and personal records you send by email or WhatsApp.

Frequently Asked Questions

Yes. The ASLI FORM PDF Lock Tool is 100% free forever — no registration, no usage limits, no watermarks and no advertisements. Lock unlimited PDFs at no cost.
By default the tool uses AES-256, the same standard approved for top-secret government data and considered computationally infeasible to brute-force. AES-128 and legacy RC4 modes are also available for older readers.
No. Encryption happens entirely inside your browser using the QPDF engine compiled to WebAssembly. Your file and passwords never leave your device, which makes the tool safe for confidential, legal and medical documents.
Yes. Because the PDF specification encrypts an entire file rather than individual pages, the tool gathers the pages you select into a brand-new PDF and encrypts that. You receive a password-protected document containing exactly the pages you chose.
The open (user) password is required to view the PDF. The owner password grants full control and lets you change permissions later. If you leave the owner password blank, the tool generates a strong one and displays it after locking so you can save it somewhere safe.
Yes. You can disable printing entirely or allow only low-resolution printing, block copying of text and images, and prevent editing, annotating, form filling and page rearrangement.
Yes. QPDF performs content-preserving encryption — it does not re-render or recompress your pages. All text, vector graphics, fonts and images keep their original quality and remain selectable and searchable for anyone with the password.
AES-256 encryption is extremely strong, so a forgotten open password cannot be recovered by us or by the tool. Always keep a copy of your password in a safe place such as a password manager.
You can lock PDF files up to 100MB. Larger files can be split first with our PDF Splitter, locked in parts, then merged back if needed.
Yes. The interface is fully responsive and touch-friendly, working on small keypad phones, smartphones, tablets, laptops and desktops. Upload from your files app, camera roll or cloud storage.
Unlike paid desktop software or upload-based online tools, our lock tool is free, needs no account, and never uploads your file. You get the same AES-256 protection and permission control as premium tools, with complete privacy and instant results.
Reach our support team by phone or WhatsApp at +91-7011993433 (Mon–Sat, 9 AM–7 PM IST) or email support@asliform.in. Every piece of feedback is reviewed and used to improve the tool.

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